Cancer continues to be a challenge for modern medicine. At a basic level, cancer occurs when there is uncontrollable cell division. The uncontrollable cell division is an effect of a break down in the natural life cycle of cells. CDK is a family of kinases involved in the cell life cycle. Abnormally high CDK activity is one characteristic of several cancers. There are naturally occurring CDK-inhibiting proteins and the abnormally high CDK activity may be due to a malfunction of the naturally occurring CDK inhibitors or due to an overabundance of CDK. CDK inhibitors are known in the art but there remains a need for additional CDK inhibitors.